"It is with a heavy heart that we share with all of you that Talia has earned her wings at 11:22am," read a message posted to her Facebook page, Angels for Talia. "Please lift her beautiful soul, her beautiful light to heaven and please send your love and prayers to her family during this most difficult time."

Talia became internet-famous by making YouTube tutorial videos that taught viewers how to apply makeup. But interweaved with makeup demos were what the teen dubbed "CancerVlogs," first person video logs in which she fearlessly looked straight into her laptop's webcam and explained what cancer treatment was doing to her body.

Talia's willingness to publicly share the complexities that harsh treatments bring was unprecedented for her age. She was a hero to fellow young cancer patients who watched Castellano list the different drugs she was taking, their side effects and how they affected her well-being.

The 13-year-old brought a voice to pediatric cancers, becoming a a role model for those who didn't have anyone else to turn to that was young, bald, going in and out of the hospital, yet remained fearless.

More than 700,000 people subscribe to Talia's YouTube channel, which she started in 2011. At the time this story was published, her channel had more than 45.6 million views. Outside her U.S. audience, her largest following comes from Brazil, Mexico and Puerto Rico, according to Talia's close friend and social media manager Christy Perry.

Talia, who lived in Orlando, Florida, was first diagnosed with cancer at the age of seven. Initially she was diagnosed with stage four neuroblastoma, a tumor that develops from nerve tissue in infants and children.

While neuroblastoma is a rare cancer with only about 650 new diagnoses in the U.S. each year, Talia used her internet notoriety to call attention to the woeful underfunding of pediatric cancer research. In 2012, Talia was featured in the documentary film "The Truth 365," which advocated more resources for childhood cancer.

Hundreds of billions of dollars are spent each year on cancer treatment and research, but the majority of that money goes to breast, lung and prostate cancer research--the cancers that affect adults most often. For every one research dollar per patient with breast cancer, a child with cancer receives just 30 cents, according to the bipartisan Congressional Pediatric Cancer Caucus that Reps., Michael McCaul (R-TX) and Joe Sestak (D-NY) founded.

The congressmen say the lack of research is partly due to pharmaceutical companies lack the ability to generate significant profit from them and fears of liability risk that they take when testing drugs on young children.

In August 2012, after over five years of chemotherapy, surgeries, treatments and multiple relapses, Talia Joy was diagnosed with a secondary cancer: MDS preleukemia. One day after she learned she would be fighting two types of cancers, Talia updated her YouTube followers.

"Having leukemia and neuroblastoma at the same time is extremely rare, not a lot of people have had that, a lot of the time leukemia comes after you've done a lot of treatment because it can be caused by a lot of chemo, a lot of radiation, which is what I have had over the past five freaking years," Talia said.

In return for her fierceness, Talia supporters helped her fulfill her "bucket list" of dreams and goals, including running a successful campaign that got her an appearance on "The Ellen DeGeneres Show."

Talia was extraordinarily wise and mature and was straight-forward when she updated her followers on YouTube. She was passionately honest and raw, in ways that most cancer support books for both children and adults alike are not.

"I'm on IV meds, I'm on a pump for Dilaudid, steroids, I'm on a few other things for anxiety that I've been having, I've been having a lot of anxiety," Talia said in her last "CancerVlog" published on May 22, 2013.

"It's adding up," she went on to say. "I can't really explain it, and I don't want to explain it, because I don't want to make it sound like something it's not. But basically, I've just not been Talia. Really down, and very anxious and moody."

When the treatments didn't go as planned, Talia would come back to YouTube and explain what plan-B was and she did it with the same confidence and hope as the first time around.

Talia's spirits remained high, even when she told her followers that her cancer was terminal and that there would be no cure.

"Having cancer has been an amazing yet horrible journey," she said. "Yet every journey has an end."